Field of the Invention
The present invention relates to a motor drive apparatus for driving a stepping motor and a control method therefor.
Description of the Related Art
Stepping motors have features such as small size, high torque, and long service life, and can easily realize digital positioning by open-loop control. Accordingly, stepping motors are widely used e.g. for information household appliances such as cameras and optical disk devices and used for office automation equipment such as printers and projectors.
In open-loop control of a stepping motor, a rotation position of a rotor of the stepping motor is detected. Generally, a current phase of a drive signal applied to the stepping motor is detected as a current rotation position of the rotor. However, there is a follow-up delay in rotation of the stepping motor relative to the drive signal applied to the stepping motor. In other words, the phase of the drive signal detected as the rotor rotation position has an error corresponding to the follow-up delay of the rotor.
To eliminate such a detection error, a stepping motor drive apparatus that detects a rotor rotation position by using a highly accurate rotation position detector has been proposed (see, for example, Japanese Laid-open Patent Publication No. 2004-180431). However, the highly accurate rotation position detector is high priced, and the motor drive apparatus using such a rotation position detector results in a substantial cost increase.